Differences
by ChocolateSyrup
Summary: After a freak accident, Hiro and Baymax (literally) learn to live in each other's shoes.
1. Chapter 1

_Alright, this is my first attempt at a multi-chapter fic! All of the others that I've written are one shots, so this is really new to me. Chapters might start out short, but I'll try and make them longer as they go. Hope you enjoy and I'd love to know what you think!_

* * *

_Why do I feel so weird...?_ Hiro wondered groggily, eyes still closed. It was as if he were paralyzed and not able to move, which was really freaky.

But that was just it. He couldn't feel a thing, except a strange and uncomfortable sort of heaviness.

Was he in the hospital for some reason? The young genius certainly hoped not.

But then again, how could he have ended up in the hospital if he had Baymax with him? The robot always made sure that he never got hurt; his health was the nurse's only concern, after all.

Hiro tried opening his eyes again, growing more worried and frustrated when he couldn't—they just seemed to be stuck together with duct tape. He laughed at the memory of teasing Tadashi about how duct tape had already been invented, but soon realized that he couldn't laugh, either.

Okay. What was wrong with him? Did Aunt Cass know? Maybe not...

The last thing he remembered was being in the lab at school with Baymax and the rest of the team. It was late, and he was working on a very important side project that he'd wanted to test out. Everyone had left when they couldn't get the prodigy to stop working, so in the end it had just been him and—of course—Baymax, who had refused to leave his side ever since the incident with Callaghan and his daughter.

Hiro assumed that he was still in the lab, so he attempted to open his eyes once more to see if he was right.

The boy sighed in relief when his eyes finally opened and he discovered that yes, he was still in said lab.

Wait. He was on the _floor_ in the lab.

Something must have happened to the machine again.

_Unbelievable. I was so close to getting it done..._

It was just then that Hiro realized he hadn't sighed at all. He wasn't breathing _at all._

A horrible thought struck him and his eyes widened.

_Am I dead?_

Panic overtook him and he grasped at his throat when hyperventilating didn't work. He was choking, but not really choking. He wasn't dying either though, which was great.

What the heck was going on?!

Hiro half expected Baymax to diagnose him with a panic attack, but he soon calmed himself down enough to realize that Baymax hadn't said anything at all about his condition, which had to be the weirdest thing ever despite the current situation he was in.

Hiro did his best to try talking through his constricted throat, looking worriedly around the empty lab at what appeared to be broken parts of his machine.

"B—Baymax...?" The teen said slowly. He blinked when a different voice came out. Had he heard right?

No, that _wasn't_ his voice. It sounded too mechanical, too programmed, too...robotic.

Hiro's eyes finally rested upon the horrifying image of himself lying on the floor a few feet away, curled up into a ball.

The fourteen-year-old genius didn't need a mirror to know what happened.

He and Baymax had switched bodies.

_Well at least I know the machine actually worked, now._


	2. Chapter 2

_Thanks for the reviews, follows and favs last chapter! I really appreciate it! Here's another one for you guys :)_

* * *

Once the shock simmered down of the fact that Hiro was now Baymax, who was now Hiro (wow, that was really confusing) Hiro knew he needed to check and see if his newly robot-turned-human was okay.

It wasn't only his new programming that told him he needed _(wanted) _to help really badly; Hiro could tell just by looking at his former body that something was definitely wrong, and that Baymax was probably having a harder time than him.

"Hang on, buddy," Hiro managed to let out in his new voice. He didn't have a mouth to move...it sounded so surreal...was this only a dream?

No. Hiro knew better than that.

The next step was getting up. He didn't even want to think about walking yet. _Come on...you can do it._

Hiro shifted position until he was on his hands and knees. If he could grin, he would have.

Why did the machine have to work so _well?_ Baymax even had his clothes on from before it happened, thank goodness. The genius supposed that he should be grateful it hadn't started a fire—or worse. _Don't think about that._

At last, Hiro was on two legs. Now to move.

He inched slowly in the direction of Baymax, trying to go as fast as he could but remembering that the original Baymax was not as fast as his human body _("I am not fast!")_ and also while avoiding broken pieces of glass.

It wasn't until Hiro was standing above Baymax that he knew for sure something was wrong—very wrong. The human's eyes were closed and he wasn't breathing.

_Oh, no._

Robotic instinct demanded Hiro to use those defibrillators in his hands, but the human side of him was having second thoughts.

Should he?

Hiro knew that he had to do _something _and fast, but he didn't know how the device would affect his body. It would also be a very rude and frightening awakening to someone who had just been turned into a human.

"Please wake up," Hiro said desperately, bending over to lightly shake the limp body.

Eyes suddenly shot open without warning, nearly knocking the genius over again. The other him gasped, glancing wildly around the room every which way, his breathing rapid.

"Woah! Calm down, buddy," Hiro said gently, relief sweeping through him.

Baymax looked up, and Hiro nearly fell over again for the second time.

It was like having an out-of-body-experience. Well, Hiro had never had one before from what he could remember, but he guessed that this was probably very similar.

"Can you hear me?" Hiro asked nervously.

Baymax nodded frantically, his breathing never slowing down. Hiro inwardly cringed, guilt washing over him. Baymax didn't deserve this.

"I need you to breathe. Can you do that for me?" Hiro said, keeping a close eye on the former robot. Baymax shook his head, grabbing at his chest.

It dawned on Hiro that robots couldn't breathe, which was why it felt like he had been (and still was) choking; he figured then that it must be a whole new ball game for Baymax.

"Breathe," Hiro instructed, making sure that Baymax was paying attention, "in and out. In and out."

Baymax followed his orders well, and soon he was breathing at the normal pace that humans should.

"There you go! You got it," Hiro praised, impressed.

Baymax hugged his knees to his chest, rocking back and forth at the awkward sensation. He never took his eyes off Hiro, most likely freaking out about staring at himself.

"I know this is really weird and scary," Hiro started, "but I have some good news and bad news. The good news is that my machine actually worked. The bad news is that it broke..." He trailed off, waiting to see if Baymax was going to say anything.

"H...Hiro..." The human-robot coughed, almost panicking again.

For the third time that day, Hiro thought he was going to fall over. Baymax actually had the same voice as him from when he was still human.

"Wh—what happened to us?"

Hiro glanced away for a moment. He could tell that Baymax was not enjoying his new voice, either.

"Well, long story short...I'm you, and you're me for the time being."


	3. Chapter 3

"What are we going to do?" Baymax asked for what seemed like the hundredth time.

"I don't know."

It was a hard thing for Hiro to admit, but that was the only answer he had at the moment.

"Do you think you can fix it?"

"I don't know, buddy," Hiro repeated, "maybe. But look at this mess. It got busted pretty bad...we're lucky to be alive."

Baymax flinched at the word 'alive,' placing a hand over his new heart. Hiro shrugged it off, knowing that it would take a long time for the robot to get used to actually being alive—the same way it would take himself a long time to get used to being a robot.

Hiro hoped it wouldn't be a long time, at least.

"I still have those blueprints somewhere. We'll just try and make the best of things until I can fix it."

Baymax nodded in agreement. "We should clean up this mess."

Hiro tried to grab Baymax by his shirt collar before he could go walking onto a sea of glass, but it was too late.

"Ow!" Baymax let out a pitiful yelp, leaping backwards next to Hiro and almost falling over in the process. Hiro managed to catch him, placing the flustered human-bot on his feet again.

"Baymax," Hiro scolded, "there's glass everywhere!" But his warning had come much too late, and now Baymax was holding his foot which had achieved a cut.

If Hiro hadn't lost his ability to sigh, he would have done so.

Baymax didn't say anything and continued trying to take care of his foot, hands fumbling over the damage.

_I guess now's the perfect time to put my new nursing skills to the test._

Hiro blinked in surprise when his programming kicked in, giving him visual instructions on how to treat a glass wound.

"On a scale of one to ten, how would you rate your pain?"

Baymax looked up at him with an expression of utter shock and betrayal, as if he were thinking, _'Hey, that's MY job!'_

"Is there glass stuck inside?" Hiro asked cautiously.

Baymax shook his head. "I don't think so, but it is bleeding..."

"Let me see."

Baymax sat into a nearby chair, lifting up his foot so Hiro could inspect the cut. It wasn't too big or serious, but it was indeed bleeding.

"I'm going to clean it," Hiro said, getting ready to spray the wound with water.

Baymax clenched his teeth, preparing for the worst.

"It won't hurt that bad," Hiro said before a sudden realization struck him: it was his robot's first time of actually getting hurt and feeling pain.

After spraying with water to clean the wound, Hiro began to prepare a special antibiotic cream. It always amazed him just how much time and effort Tadashi had put into Baymax. He knew that the robot had been programmed with over 10,000 medical procedures, and now he was experiencing his brother's handiwork first-hand; Hiro was just surprised that he wasn't exploding from all the codes and information.

"You know, this is pretty funny," Hiro said, attempting to make conversation as he applied the ointment.

Baymax frowned, not finding any humor in the situation.

"I do not find this funny at all."

Hiro wished he could roll his eyes.

"I mean, it's funny because usually you're the one taking care of me. Now I'm the one taking care of you."

Baymax obviously didn't like that idea.

"You are still my patient," he stated simply.

"There! All done," Hiro said, stepping back to admire his work. The cut was now taken care of and no longer bleeding, along with a colorful band-aid added for the finishing touch.

"Have a lollipop." The ex-human hadn't even realized that a lollipop was in his hand.

Baymax held his foot with a grimace.

"It might be sore for awhile, but I think you can walk on it," Hiro said, throwing the lollipop away. It probably wasn't a good idea for Baymax to start eating yet.

He watched Baymax continue to sit on the chair anyway, still keeping a firm hold on his foot. Guilt seeped through him once more.

"I'm really sorry about all this, Baymax," Hiro apologized with complete sincerity, "but I promise I'll do my best to fix that machine. We'll be back to our normal selves in no time."

Before Baymax could respond, a door was heard opening and closing.

"Oh man, I forgot about Aunt Cass!"

Panic nearly overtook him again, but he knew he had to remain calm for Baymax.

"We were here too late, and now she's coming to pick us up. Just act natural..."


	4. Chapter 4

_Thanks for the reviews last chapter! I'm glad everyone's enjoying this story so far (I think xD) But I really do appreciate it! :)_

* * *

Aunt Cass was absolutely horrified when she stepped into the lab and saw shattered glass all over the place. The look on her face clearly told Hiro that she was ready to race right over to them and give "him" a shower of hugs and kisses.

He was grateful that the glass prevented her from doing so at first; he knew Baymax wouldn't be able to handle a suffocating hug, especially not when the only sort of touch he'd experienced so far that night was being patched up after hurting his foot.

"Hiro!" Aunt Cass exclaimed, doing her best to avoid the glass. "What happened in here?! Are you alright? You were supposed to be home hours ago!"

Hiro nudged Baymax with his arm when he didn't answer her right away.

"Yes, Ms...Cass. I am alright."

It would be out of character for Baymax to facepalm, so it took a lot of willpower for Hiro not to do just that.

"Huh?" Thankfully, Aunt Cass was distracted by the glass under her feet.

When she finally made her way through, Hiro's aunt looked up and her eyes widened when she saw Baymax sitting on the chair.

"Hiro, your foot!"

Baymax gripped his foot tighter, trying not to make her even more worried than she already was. That was the opposite of what he was supposed to do, after all.

"I am fine, 'Aunt' Cass. Hir—Baymax took care of it for me."

Aunt Cass tilted her head in confusion at his odd choice of words. "Are you sure you're alright, sweetie?"

Hiro figured that now was a good time to intervene and help.

"He seems to be suffering from lack of sleep, Aunt—Ms...Hamada. I suggest that we bring him home so he can rest." _Great._

Aunt Cass stared at him for awhile, raising an eyebrow. Hiro stared back and blinked his robotic eyes for good measure. Baymax just watched, almost amused, as a staring contest unfolded.

Aunt Cass gave in and sighed. "Both of you look like you need rest...I'll clean up so we can get out of here faster. Hiro, you stay seated—I don't want you cutting your foot again. Please keep an eye on him, Baymax."

_Oh, I have been._

* * *

Once Aunt Cass was done cleaning the lab, the first thing she did was nearly squeeze the living daylights out of the poor human.

"Never do that again! Hiro, you really had me worried. What if something happened to you?"

_Something did,_ Hiro thought dully. He kept quiet, watching as Baymax went into a coughing fit thanks to the hug. Aunt Cass quickly released him.

"I'm sorry! It's just—let's get you home. You need to rest; sometimes I wish you wouldn't stay up so late working on your projects. It's almost midnight!"

Hiro wasn't sure why his aunt had been so worried about him. He'd stayed up even later than midnight before—almost to the crack of dawn a few times, especially when working on his microbots. He suspected that it was because of Baymax's peculiar behavior in his body, and it stressed her out.

Then she gestured to Hiro. Baymax followed her signal and froze when his eyes landed on the former human.

"You have to pack him up so he can fit in the car," Aunt Cass explained wearily, knowing that Hiro sometimes flew Baymax home after school instead of taking the bus or walking with his friends, "I don't want you flying in the dark while you're tired and while he's...well, I think he's malfunctioning."

Hiro would have blatantly taken offense to that comment, but a blank numbness buried his emotions.

Baymax walked up to Hiro in slow motion on wobbly legs until he stood in front of the human marshmallow. Meanwhile, Aunt Cass fretted that her little college man was just too overtired.

Hiro cocked his head, trying to let Baymax know that what he was about to do would be okay.

But it wasn't okay, because Baymax was going to say 6 words that Hiro had vowed never to use again after what happened in the portal.

"I am satisfied with my care." _It felt so wrong._

Hiro had no choice but to comply and, for the first time, he deactivated.


	5. Chapter 5

"Owwww...?"

It was as though Baymax had never made him deactivate at all, like he'd fallen asleep and woken up, but without dreaming. All he remembered was Baymax telling him to deactivate, and then...black. That was it.

His machinery lurched as he re-inflated and grew back to his robot's normal, giant marshmallow size. He could see Baymax waiting for him, and apparently they were back in his room.

Hiro started to speak, but the voice of a certain robotic nurse interrupted.

"Hello. I am Baymax, your personal healthcare companion. I was alerted to the need for medical attention when you said 'ow.'"

Baymax gaped, fearing the worst for his patient. Had Hiro's human nature been...overwritten? Just like that? Hiro never should have been deactivated, not when they didn't know how it would affect him yet! The heart in his chest thumped faster. He didn't like the feeling of fear.

"Sorry, buddy. I just have to get through your natural programming, first."

Baymax slumped his shoulders in tired relief, suddenly wanting to give Hiro a good punch for scaring him. Wait...where had that come from? The last thing he wanted to do was hurt people, especially Hiro. Human emotions were so confusing.

"...You almost gave me a heart attack."

Hiro walked off of the charging station and Baymax sighed, going to stand in front of his human's bed.

"So...how was the ride home?" Hiro asked. It looked like Baymax hadn't blown their cover; Aunt Cass had to be asleep by now.

"Ms. Hamada was doing all the talking, if that's what you're asking," Baymax responded plainly as he stared at the bed before him. It looked so inviting, but it just wasn't right.

Hiro noticed and went to stand next to him, deciding to put off telling Baymax that he should really practice calling Aunt Cass...well, 'Aunt Cass' if he was going to be stuck in his body for awhile.

"It's okay, Baymax. You really do need to rest. It's been a long day."

Baymax looked up at him for permission once more, and Hiro gave him a small nod.

* * *

"How do humans sleep?"

The lights were turned off save for one, and Baymax was finally comfortable for a change (after an interesting trip to the bathroom, that is.)

"Uhhh...just close your eyes and try not to think about anything. My—I mean—_your_ body will know what to do," Hiro explained by his bedside.

Robots didn't need sleep, so Hiro had no idea what to do with himself besides charge and keep watch over Baymax.

"It's so strange..."

"Yeah?" Hiro asked, curious to know how the bot had taken his first day as a human.

"I feel trapped, yet...free at the same time."

"...That makes sense."

When you're a robot, you have to follow orders from your master or creator no matter what. You have to follow the protocols programmed inside you without question. You don't even have feelings.

When you're a human, you have feelings. You have to listen to what your body wants and needs—a little like programming—but it's not the same when you don't have protocols telling you what to do and how to do it every second.

"And Tadashi..."

Hiro didn't know what to make of that.

"—You were right...it is a different kind of hurt..."

Then Hiro understood. Tadashi was his creator, and Baymax was experiencing the first pangs of grief as he looked at his brother's empty bed.

Hiro was about to offer a physical form of comfort, but decided against it. Baymax was still getting used to touch after just a few hours of being human, and even feeling warm and cold. Though his bed was comfortable, he could see the ex-robot squirming against the covers every once in awhile.

"I wonder what he'd say about all this," Baymax said sadly as he felt something wet roll down his cheek.

"'Looks like you're really seeing things from a new angle this time, knucklehead,'" Hiro guessed aloud, trying to help Baymax feel better. He himself only felt hollow, and that scared him somewhere in the back of his mind.

A growling sound was suddenly heard. Baymax sat up in a flash, eyes wide.

"And that hurts too, but it's a physical kind of pain!" Baymax exclaimed, holding his stomach. "What was that?!"

"Shhhh!"

Hiro hadn't eaten much that day out of determination to finish the machine, and it was just settling in.

"What do you say, buddy? Up for a little midnight snack?"


	6. Chapter 6

Hiro decided that a milkshake would be best for Baymax to start out with. A milkshake wasn't hard so he would have to chew, and Hiro didn't want him to do that yet for fear of choking (which he was still getting used to.)

The milkshake was easy to make in the upstairs kitchen; it was just difficult maneuvering behind the counters and table in his current body.

As Hiro got the milkshake ready, Baymax was thrilled to find that he could actually pet Mochi, the 'hairy baby.'

Mochi obviously knew something was up the way "Hiro" was acting—and he just _had_ to hiss at Baymax when they first met in his new form—but now the two of them were practically inseparable. He sent the real Hiro death glares every once in awhile, still mad at his owner for being thrown up the stairs.

"He's so soft," Baymax commented, marveling Mochi's fur as he sat at the table.

"Soft maybe, but definitely not cuddly," Hiro remarked. Another death glare. _Darn cat._

Mochi jumped off of the table, and Hiro set the milkshake down.

"Use the straw to drink," Hiro said, "take small sips first—we don't want another trip to the bathroom."

Baymax, albeit awkwardly, took hold of the straw in his mouth and sucked. Within a second he sputtered, coughing the straw out.

"On second thought, maybe a spoon would be better."

* * *

Once Baymax got the hang of holding a spoon, he finally had the chance to try his first taste of human food.

"What do you think, buddy?" Hiro asked curiously, watching as Baymax lifted the spoon with a shaky hand to his mouth, swallowing the white liquid. He almost coughed again as it went down, but managed to keep it in. His eyes lit up and Hiro took that as a sign that he was enjoying the shake.

"Don't give yourself a brain freeze," Hiro warned when Baymax gained enough courage to eat a little faster.

Too late.

The bygone robot grabbed his head, squeezing his eyes shut in pain.

"It'll pass!" Hiro said quickly when Baymax looked like he was on the verge of panicking. "Just give it a few seconds."

Baymax continued holding his head until the seconds ticked by, and the sharp cold went away. He looked at the milkshake as if it were something out of a horror movie that Aunt Cass would sometimes watch.

"It won't happen again as long as you eat slow," Hiro reassured him, placing a hand on the human's shoulder. Baymax recoiled and Hiro jumped back, surprised that he'd forgotten so soon.

"Sorry! I didn't mean to!" Hiro quickly apologized. Baymax managed to stop the milkshake from taking a spill, steadying the table. He didn't even realize that he was holding his breath as they waited for Aunt Cass to make an appearance after the ruckus, slowly letting it out when she never came.

"...No, it's okay. Don't worry."

"Nice save," Hiro complimented. Baymax smiled and returned to finishing his milkshake.

* * *

"We can't tell anyone about this, Baymax. Maybe the team, but I don't even think _that's_ a good idea."

Baymax looked up at Hiro, shocked. "What? But don't you need help fixing the machine?"

Hiro shook his robotic head.

"I didn't really have any help the first time. Besides you, that is," he added quickly when Baymax frowned, "it was supposed to be a surprise for Fred. Not one of my greatest ideas I know, and I see that now."

Baymax crumpled his face in confusion. "Really? You never told me that."

"That's the point of surprises...I just don't think it's a good idea. No one would believe us."

Baymax blinked, confusion never wavering. "Why?"

"Our voices are the same as they were before. Well, before it happened. They'd think you're crazy and that I'm...malfunctioning, like Aunt Cass said. We'd never get back to normal."

"What do you mean?"

"Listen, Baymax...as far as I know, nothing like this has ever happened in the history of San Fransokyo—maybe the _world._ If someone besides the team ever found out and had bad intentions, like Callaghan, they'd use us as guinea pigs—and not the hairy baby kind. Do you understand?" Hiro didn't mean to sound harsh (even though his voice carried the same cybernetic tone) but it had to be something to take under consideration.

Baymax stared down at his empty glass. Hiro had brought up a good point, and that point scared him almost more than being stuck in his patient's body.

"I understand, but...I think we need to tell your friends. They would believe us, and they can help."

Hiro got ready to clean up the table.

"...I'll sleep on it."

Of course, it was hard for Hiro to sleep on it when he couldn't sleep, and when Baymax woke up screaming at 3 in the morning because of a nightmare.


	7. Chapter 7

"Was it about the fire?"

_There was red everywhere._

Aunt Cass had woken up hearing Baymax scream. She sat next to the human-bot on Hiro's bed, trying her best to understand. Hiro had been doing so well, lately...

_It was as though he had been deactivated. There was black at first, but then the black was replaced with red._

"Y...yeah." Baymax hated lying. He would never lie in his previous form, but then again, he had never been programmed to lie. His speech slurred a bit as he tried to say words the way his patient would.

_The robot only had one mission to complete, and he intended to complete that mission no matter what (or who) got in his way._

She sighed, placing a hand on his forehead to wipe away a stray hair. He winced at the touch, but allowed her to do so. She noticed his jumpiness. "I think it's best if you don't go to school today. You were up late last night, your foot is cut and now the nightmare..."

_The red nearly clouded his vision to the point where he could no longer see the fear on the man's face before him._

Aunt Cass didn't want her nephew to experience those horrible nightmares again. He hadn't had one this bad since Tadashi...

_His target was trying desperately to get away, but he wouldn't let him. He charged._

"I am in agreement with Aunt—Ms. Hamada," Hiro stated, mentally slapping himself for messing up her name again, "it would be wise for Hiro to take a small break from his academic activities. He would not perform well today." Or possibly ever. As much as they needed to get back to the lab, it would be a disaster if Baymax was accidentally thrust into college life.

_The only thing that stopped his target from being annihilated right then and there were shorter figures pushing up against him, trying to make him stop._

Hiro also wanted to emphasize _small,_ as it was crucial for them to go to school so he could work on the machine, but unfortunately there wasn't much he could do about emphasis.

_He flung them aside without hesitation._

Aunt Cass raised an eyebrow at him for the second time.

_The man was close to escaping, but the mission had to be completed no matter what. Still, he gave chase._

"Once you're feeling better, sweetie, it sounds like he could use a few tune-ups," Aunt Cass suggested, chuckling as she attempted to make Baymax smile. He nodded slowly, but refused to look up at Hiro. The thought of "fixing" his patient disturbed him almost more than what he had just experienced that night.

_He couldn't stop._

Aunt Cass rose to her feet, tiredly rubbing her eyes as she walked towards the door.

_He __**wouldn't**__ stop, not until he terminated his target._

"I'll take care of the school and let them know in the morning. Well, later today. You go on back to sleep if you can."

_The red disappeared._

Baymax waited until she was completely gone to lie down. He curled up into a fetal position, covering his face with his hands; he obviously wasn't going back to sleep anytime soon.

_What happened?_

Hiro reached forward to try and console the shaken robot.

"Baymax—"

"No!" Baymax interjected, his body trembling.

"You told me to—I almost _did—__**why...?"**_

It broke Hiro to see Baymax so upset for the first time (and because of _him._) The bot's nervous behavior nearly drove his scanners up the wall.

The genius blanked for a moment, unable to ward off his robot's protocol.

"Your blood pressure and heart rate have increased dramatically," the instinctive voice said.

Baymax wasn't supposed to have a heart. He wasn't supposed to be lying there alive, stuck in a human body and in _his_ body, no less. He wasn't supposed to remember that horrible night when his patient had commanded him to destroy professor Callaghan, overwriting Tadashi's medical chip.

_I regret any distress I may have caused._

"I hurt them..."

Everything was all wrong, and Hiro drowned in the fact that it was because of him and his stupid mistakes. He had to fix this, and fast.

So Hiro did the only thing he could think of doing.

He contacted the Big Hero 6.


	8. Chapter 8

_Thank you everyone for sharing your thoughts last chapter and asking for more, so here's more :D_

* * *

"So let me get this straight. That's not Hiro sleeping in his bed?"

Wasabi was entirely confused, simply put.

The gang had wanted to come as soon as possible once they received Hiro's message, but college was important; they had to wait until classes were over.

Hiro had spent most of the day attempting to comfort the robot that it was just a bad dream, but Baymax knew better and refused to speak to his creator's little brother. It took awhile, but the former bot eventually fell back into a peaceful enough sleep.

"No. It's Baymax," Hiro replied firmly as he could, watching as the team eyed him and the former robot. They glanced back and forth, concerned and unbelieving.

"Hiro, what...what happened to you two?" Honey Lemon asked, carefully approaching the ex-human. She looked him up and down, trying to make sense of things. Hiro was definitely a lot taller than he was before, and...chubbier.

"All I remember was working on one of my inventions. It wasn't really ready to be tested out yet, so it must have exploded. We were caught in the middle of it."

Honey Lemon gasped. "That's horrible! I knew we shouldn't have let you stay so long!" Somewhere behind the dark eyes of Baymax, she could see her friend struggling underneath the mechanisms of Tadashi's creation.

"What exactly did this machine of yours do?" GoGo questioned, grabbing Fred by his arm when he tried to go over and inspect the sleeping human.

Hiro looked over at Baymax, recalling the unpleasant time when they first woke. "Long story short...we switched bodies. It was an accident. You have to believe me..."

"Why wouldn't we believe you?!" Fred piped up. He lowered his voice to a whisper upon the others' instruction, not wanting to wake the sleeping bot.

"—This is amazing," Fred whispered, "amazing and weird at the same time! But mostly amazing. And Honey said it wasn't science."

Honey gave Fred a small frown. "It's really not," she defended quietly, "just look at what happened! This isn't good for either of them."

"Honey's right," Hiro agreed, "I messed up really bad this time. We need your help, guys..."

"What do you need us to do?" Wasabi asked, already determined to lend a helping hand.

Hiro knew then that he had made the right choice in letting his friends know about their problem right away, and that Baymax was a good judge of character. He would have felt sorry for doubting his friends—Tadashi's friends, but no matter how much he tried expressing emotion, it continued to be shoved aside by the robot's tech.

"I need the blueprints for the project—and they're at school in my lab," Hiro began, inwardly cringing at calling Tadashi's lab 'his' lab. It was one of those things that he had never gotten used to since the accident. "Aunt Cass didn't want "me" going today because of everything that happened last night. Baymax cut his foot on glass and had a nightmare."

"Does she know?" GoGo asked, glancing at Baymax. It was all so crazy. He looked exactly like Hiro, and Hiro looked exactly like him. Worry was pinching at her somewhere in the gut, but she couldn't let it get to her.

Hiro concentrated, trying to show her an 'are you kidding me?' type of face. All he managed to pull off was a blink, as usual. "If Aunt Cass found out, she'd probably faint and have a heart attack. You guys can't let anyone else know about this, okay?"

Honey Lemon nodded, understanding that terrible things could happen if those blueprints fell into the wrong hands or worse—if someone found out about Hiro and Baymax.

"Woah, he can dream and get hurt?" Fred asked incredulously, making another attempt to go and have a peek at the sleeping Baymax. GoGo stopped the science nerd immediately, yanking him harder on the arm. Fred paid her no mind, his attention snapping back towards Hiro.

Hiro tilted his head to the side, giving the crew another blink. "He's human now, guys. He has thoughts, feelings and emotions like you or me. Well, I used to."

"Uhhh, what do you mean by that?" Wasabi's concern rose tenfold. If he hadn't seen a certain something at Fred's house or had a man in a kabuki mask attack him and his team, he decided that this just topped all of the other weirdness he'd seen in his life.

"Nevermind," Hiro responded, not wanting to worry his team further, "we just need to concentrate on getting those blueprints for now."

"We were worried when you didn't come today," Honey Lemon said, placing a hand on Hiro's shoulder. It felt just like the original Baymax; plastic. Fred couldn't help himself, taking the opportunity to try and pinch a vinyl arm. GoGo shot him a disapproving glare.

"Thanks, Fred," Hiro quipped, "that was sarcasm, by the way." Fred gaped as Hiro seemed totally unaffected by the pinch. Hiro just hoped he wouldn't have to tape his arm back together should air start pouring out of it. He didn't want to know what that would be like.

"Look," Hiro said, stealing a glance at Baymax. The robot was beginning to stir. "He had a nightmare last night about me telling him to destroy Callaghan...I think it'd be better if you're not here when he wakes up."

GoGo understood, nodding to the rest of the team. "We get it."

"I really do appreciate you guys for coming...and not freaking out."

"Oh trust me, we freaked out," Wasabi said, a subtle look of disturbance crossing his features. "Still freaking out," he added on the way out the door.

"We'll get you those blueprints tomorrow, man," Fred announced with renewed vigor and determination.

Honey Lemon let go of Hiro's shoulder and nodded to confirm Fred's statement before leaving behind him. Soon, Hiro was left alone in his room with only Baymax to keep him company. He went to stand by his bed, waiting for the human-bot to wake up.

* * *

"Come on buddy, you gotta talk to me sometime," Hiro pleaded when Baymax refused to answer, pulling covers over himself with his eyes still closed.

The teen's worry continuously grew when yet again, not a sound was heard from the former bot.

Hiro was just about to grab the covers and pull them away when a tiny, weak and tired voice finally answered.

"...I don't feel good..."

Before Hiro knew what was happening, a simple scan confirmed that Baymax had a fever.


	9. Chapter 9

Hiro had never thought that he would hear a robot say _'I don't feel good' _in his lifetime; let alone a healthcare nurse.

"Well, you definitely have a fever," Aunt Cass said as she pulled a thermometer out of Baymax's mouth. She hadn't exactly trusted Hiro's diagnosis of a cold, seeing as how he was currently 'malfunctioning.'

The human-bot had to stop himself from gagging when she first put it in, completely surprised by the sudden intrusion and taste of the thermometer. He eyed Hiro when the little stick was pulled out, face clearly sending the message of _'never again.'_

"It was nice of your friends to drop by and check on you," Aunt Cass noted as she got up from Hiro's bed.

Baymax continued eyeing Hiro, his stomach jumping. _They did?_

"Yeah..." He said slowly in response to Aunt Cass.

"Looks like you won't be going to school tomorrow, either. I'm sorry that you have to miss two days," she said with a solemn smile, "but at least tomorrow is Friday. You'll be better by the time the weekend is over."

Baymax nodded.

Hiro couldn't help but be amused by what Aunt Cass had said about being better 'by the time the weekend was over.' Sure, his friends would get the blueprints, but then there was the issue of actually starting to rebuild the machine. That would take some time, as much as he hated to admit it.

"So what can I get you for dinner? Those hot wings of ours always seemed to help you out before when you've had colds like this."

_Please, no._

Baymax apparently knew that he wasn't ready for hot wings either, politely turning them down.

"May I suggest chicken noodle soup?"

Aunt Cass turned to Hiro, eyeing him suspiciously and weighing the options of whether or not to take the suggestion of a malfunctioning robot to heart.

"That sounds perfect," she agreed after a long pause, "I'll be back soon."

* * *

"So you told them?"

"Yeah. They're gonna get the blueprints from school tomorrow. I'll look them over so we can get a better grip on things."

Baymax gave Hiro a weak smile, glad that he had decided to trust his friends; at least now they had some help and weren't so alone.

"What is it?" Hiro asked when the robot's face fell.

Baymax didn't answer, lowering his gaze.

Hiro instantly got the message, attempting to formulate a route of comfort.

"It's okay, buddy. They understand...don't beat yourself up over it."

Baymax looked away, guilt still tearing at him. He couldn't shake the feeling away, like it was latched onto his very being and refusing to let go.

"They don't blame you, Baymax," Hiro tried reassuring, "it was all on me...I never should have done that to you."

Silence prevailed for a few more moments.

"Hiro?" Baymax whispered so softly that Hiro almost couldn't hear.

"Yeah?" Hiro noticed that the bot was shivering, unable to get warm even though covers were still wrapped around him. _Must be the chills._

"Am I going to die?"

Hiro wanted to laugh, still not quite used to the fact that he couldn't.

"No, buddy. It's just a cold. While they're not the greatest things in the world to catch, it'll pass. Just like a brain freeze!"

Hiro supposed that was one of the advantages of being a robot; you couldn't get sick...or die. You could eventually break down, but that would take a long time with the way technology was advancing. The thought suddenly haunted him that if he—by some chance—couldn't get the machine fixed in a decent amount of time, something bad could happen to his companion—and in _his_ body.

Baymax seemed befuddled, bringing Hiro back to reality.

"That fast? And colds are like balls?"

"Not exactly."

"Just an expression?"

"Right. Just an expression."

Speaking of advantages, it was then that a crazy idea popped into Hiro's head. It was a stretch, and they had to concentrate on getting the machine done, but maybe the idea would help the bot feel better and give Baymax something else to look forward to (besides turning back into a robot.)

"Hey. Maybe when you're all better, I can try out that rocket fist of yours and learn those karate moves. I bet Fred would love that."

"...Maybe we can fly, too."

Apparently Baymax was crazier than him, but he attested.

"Alright. You teach me karate, I take you flying."

Baymax laughed, a coughing fit erupting. Hiro realized that it was the first time he'd heard Baymax laugh since he turned human.

"Deal."

Aunt Cass returned with a bowl of chicken noodle soup, placing it atop a little table so Baymax had something to eat off of. Luckily, she decided to say goodnight so that unawares to her, Hiro could help Baymax not have noodles go up his nose.


	10. Chapter 10

"Why did I ever invent this stupid machine?"

Hiro gazed at the blueprints before him. Of course he knew why he'd invented the machine. Fred had given him the idea when they'd first met, although the science enthusiast didn't know it.

_"I've been trying to get Honey to develop a formula that can turn me into a fire-breathing lizard at will, but she says that's 'not science.'"_

It would have been near impossible to achieve what Fred had actually wanted (since fire-breathing lizards didn't exist) but Hiro had come up with the next best thing: why not a machine that could switch bodies?

The young prodigy had never had any intention of actually putting the idea to use until the Big Hero 6 came about, figuring that it would be a good, harmless side project to try and prove Honey Lemon wrong.

Well, he _thought_ it would be harmless at the time.

The gang had dropped off the blueprints soon after school ended, as promised. Hiro advised them not to go anywhere near Baymax unless they wanted to catch his cold, but they insisted and wanted to see him anyway.

Fred made a random and (slim) but possibly plausible point that maybe since Baymax was originally a robot, he wouldn't be contagious to normal humans.

Hiro turned his gaze to the group, watching as they interacted with Baymax. The human-bot seemed okay with such a big crowd looming over him, but Hiro could tell he was still nervous.

"Give him some space, guys. He's not a science experiment."

"Sorry," Honey Lemon apologized, taking a step back from Hiro's bed, "we just have so many questions!"

"It's alright, Hiro," Baymax said, holding a scratchy throat, "perfectly understandable."

"Don't blame me if you guys get sick."

"Hey, maybe my theory will turn out to be correct," Fred responded wistfully, attempting to poke Baymax in the arm once again. "Did that hurt?" he asked Baymax curiously. The robot had to resist the urge to swat his hand away.

"If only we knew why the machine broke in the first place. Then I'd know what not to do again and make it better."

"You instructed me to record the project's completion," Baymax suddenly mentioned when the thought occurred to him.

"I did?" Hiro faintly recalled doing so, wanting to record a pivotal moment in his invention history.

It was like second nature as he accessed the video files. Was this what it was like for Baymax when he'd shown him the videos of Tadashi?

The team waited anxiously as the video started to see the reason behind why the machine had failed. Baymax sat on the bed in a sort of stupor as he looked on, every once in awhile swatting Fred's hand away.

_"...This is Hiro Hamada, and this is the 73rd test of my SWAP project. It's not ready yet, Baymax. I just need to tweak a few things first."_

_Hiro held a subtle look of tiredness. It was almost midnight, after all. He was just happy that the team had left so he could finish faster._

_A few add-ons here, a few tweaks there. It was almost done. If only he could just..._

_"Hiro!" The cry of Baymax sounded._

_Noise. An explosion._

"...Woah," was all Fred managed to get out.

"Remind me not to rebuild the case with glass," Hiro muttered plainly, glancing at the blueprints.

"How did you get out of that without a scratch?" Honey Lemon gasped. Even GoGo was shocked that the machine had caused that big of an accident.

Wasabi was even more amazed at the fact that Hiro and Baymax survived.

Hiro knew why he'd lived through such an ordeal. He turned to Baymax, forever grateful for the robot's constant watchfulness.

"You saved my life."

Baymax snapped out of his contemplation. "It was in my programming to help and not allow harm to come to my patient. Your health is my only concern."

Hiro shook his head. He didn't like the fact that Baymax saw him as only a patient and nothing more, even as a human. It hurt him more than the bot had realized back in the portal.

But it didn't make any sense...he hadn't even realized that there had been something wrong with the machine before it exploded on him.

"At least we know how you two got swapped now," Wasabi commented, glancing at Baymax in amazement. If the robot hadn't been there...

"Uh, guys?" GoGo interrupted, "It's great that they survived and all, but Hiro said that it took...what, 73 tries for him to get that far with the machine. Which took you how long, Hiro?"

Hiro paused, reality punching him in the face. "Uhhh...three months."

Fred's eyes widened.

"...Woah."

Baymax cradled his knees to his chest, rocking back and forth. Hiro was reminded of how he couldn't breathe soon after turning human.

"No, no, no, buddy...calm down," Hiro said quickly, immediately going over to help the startled bot when his sensors picked up a panic attack approaching. "It won't take that long this time. We have everyone here to help us."

Baymax looked up at him with a hopeful expression, managing to calm himself down. Breathing still hurt. It burned and with his sore throat, the air hurt even worse.

"We'll do whatever we can to help," Honey Lemon promised. She wanted to give Baymax a physical form of comfort, but refrained. He'd been through enough already.

"I second that," Fred agreed. GoGo nodded in confirmation that she was in, too.

"...Thank you," Baymax said softly, covering his mouth when a cough escaped.

"Hiro?" Wasabi asked when the teen didn't answer.

Hiro blinked, snapping out of an unsuspecting daze.

"You spaced for a minute there, man," Fred told him with a bit of worry in his voice.

"...I'm fine. Just lost in thought."

GoGo eyed the genius warily, not believing it.

"We need to get this thing started."


	11. Chapter 11

Three weeks passed.

Hiro was trying to keep a level head. He had to, especially for Baymax. His sensors indicated that the human's neurotransmitter levels were dropping slowly every day that the machine wasn't done.

Said machine wasn't even 20% done.

The team was trying their best to help get it finished under Hiro's supervision. They were worried that the longer he and Baymax stayed the way they were, the bigger the chance that they wouldn't be able to go back to their normal selves at all.

Miraculously, Fred's theory that they wouldn't catch Baymax's cold actually turned out to be true. None of the Big Hero 6 became sick or had a fever the following week after visiting Baymax, which Hiro was grateful for; they had to help with the machine.

College stopped them from working every once in awhile, of course. The team tried to work on the machine a little every day, but it was still a thorn in the side. Even so, Hiro couldn't blame them for wanting to pass their classes. Sometimes they brought their homework along to work in the garage, but even that slowed them down.

The gang also vouched for Hiro when the school started asking if he was better and where he was. They claimed it was another "family emergency" and that he needed some time to recover. Their new professor seemed to understand and bought it, politely leaving them to their business.

Aunt Cass had no idea what was going on. Since she suspected that Hiro was still going to school after feeling better, Baymax had to stay cooped up in the garage where the café owner rarely went (unless Hiro needed something to eat) so he wouldn't be seen by her and cause more problems.

A bright light shone one day when Baymax remembered his deal with Hiro about learning karate. Hiro agreed and Baymax told him that he already knew all of the moves and just needed someone to tell him what to do. The bot wasn't fond of giving his patient orders, so Fred cheerfully volunteered and Hiro was able to do every kick or hit that he had previously downloaded into Baymax.

Baymax was happy for awhile after the karate lesson, but his levels didn't stay up for long. The bot simply needed his job of healthcare companion back, not knowing what to do with himself if he couldn't live up to his programming.

"Baymax?"

The human-bot spun around in his chair to face Hiro, giving him a downcast smile.

"You need to eat something, buddy."

Baymax frowned at the plate of cheese and crackers that Hiro had brought from the kitchen with Honey Lemon's help. The chemist had left soon after to go to school. The only Big Hero 6 member in place was Fred, who had kindly decided to drop mascot duties and feign being sick to keep Baymax company. GoGo had promised that she would try and get out of classes a little later in the day.

"I'm not hungry."

A quick scan revealed otherwise.

The bot had managed to get the hang of eating solid foods less than a week after turning human. The first time had not been so pleasant, what with slippery noodles mixed with chicken in broth. He had enjoyed the meal nonetheless, but still preferred milkshakes over anything chewy.

"Baymax..."

He couldn't live on milkshakes.

"I don't like eating," the robot said firmly, gently pushing the plate away when Hiro set it down on his work space.

Fred stood nearby and his eyes widened at the fact that someone was blatantly refusing free food, even saying that they did _not_ like food. Hiro sent him a hint not to get involved.

"Please. Do it for Mochi or he'll get it first," Hiro said when the cat made himself known and began poking his nose into the cheese.

Baymax watched as Mochi began to nibble. He knew that human food wasn't good for animals, reluctantly taking the plate away. Mochi meowed and eyed him irritably, sitting on the desk and swishing his tail back and forth.

The cheese and crackers remained untouched in the bot's lap.

"Maybe I can do the airplane thing with him again," Fred whispered to Hiro. The genius shook his head when an unexpected episode occurred.

"Your hormone and neurotransmitter levels indicate that you are experiencing mood swings, common in adolescence. Diagnosis: Puberty."

The sound of the garage door opening and closing snapped Hiro out of it. Judging by the looks of Fred and Baymax, he'd said something completely awkward.

"I'm here," GoGo called. She stopped when the three faced her with perturbed glances.

"What'd I miss?"

Baymax gave her a flustered smile, face turning red.

"Nothing exciting," Hiro replied quickly. Fred laughed nervously and took a step back.

"Uhhh, what he said."

"Okay...so I'm gonna go start working."

Fred nodded. "I'll help."

* * *

"So, what? If it hadn't been programmed, you never would have saved me in the first place?"

Hiro hadn't meant to start a full-on argument. Baymax had continued refusing the food and burst when Hiro pleaded him to at least take a few bites.

"Maybe not! Then we wouldn't be in this mess!" Baymax flared, his eyes red and teary.

"We wouldn't be here at all, then!" Hiro argued, pressure building inside his gears. He was sure something was going to snap. If only he could raise his voice higher. "Is that what you want instead?"

Fred and GoGo looked on in shock at the fact that Baymax was actually angry. Hiro had witnessed his first bout of anger when he remembered what happened during the Callaghan incident, but the two had never witnessed him upset until now.

"Guys," Fred said calmly, stepping in between the torn duo.

They continued to argue, Baymax shouting louder.

"This is all your fault!"

"Yeah, it's my fault! But you know what? It's human to make mistakes. Something you wouldn't know anything about _**because you're not human!"**_

"That's the problem!"

"You don't get it!"

Fred knew that if he couldn't stop the fight soon, Aunt Cass would hear the yelling.

"I have a question!"

"What?!"

"Have you tried flying yet?"

GoGo sighed. "What kind of question is that? Do you want them to crash land and die?"

A light bulb switched on. Why hadn't the prodigy thought of that before? "No, no...we actually talked about it already."

"Really?" GoGo deadpanned.

Hiro swiveled his head back towards Baymax. The bot was sitting back in his chair at the desk, covering his face with his arms.

"Baymax...I'm sorry. I didn't mean—"

"I'm sorry, too. I didn't mean it, either," the human-bot mumbled without looking up.

"I think flying would do us some good," Hiro suggested thoughtfully, "maybe raise those neurotransmitter levels of yours."

Baymax glanced up at last, his face still red from screaming. "Are you sure?"

Hiro nodded. "We need a break from...all this."

Baymax gave him a real smile for the first time that day—possibly in weeks—his face slowly turning back to normal.

"But only if you eat something first," the genius cut in, pointing to the uneaten plate of cheese and crackers.

Baymax sighed, hesitantly robbing the plate from Mochi once again.


	12. Chapter 12

_I would again like to thank everyone who has reviewed, followed and/or faved this story! Or just read this story in general so far! It means a lot to me; I'm having a ton of fun writing it all out and I'm glad that there's someone out there having fun reading it :D_

* * *

"You sure you still want to go through with this?" Baymax asked nervously as he and Hiro walked through Fred's backyard in their flying suits. It was the only place Hiro could think of to do their test flight, remembering the first time he and Baymax had taken off. Fred had happily agreed to lend them his property once again, even though Baymax had previously destroyed the garden wall with his rocket fist.

If Hiro could feel, he was sure that the red suit would feel like a never-ending pile of bricks and that he would be crushed underneath the weight. Thankfully, he could now lift 1,000 pounds.

Baymax scratched at his purple armor, still getting used to wearing something other than a sweatshirt. It had definitely taken a long time to get the suits on, but Hiro was certain that it would be worth all the trouble.

"When have I ever _not_ been sure about flying?"

Hiro looked up at the setting sky, wondering just what he was getting himself into.

"Yep, he's nervous," GoGo commented decisively.

"I am a robot. I cannot be nervous," Hiro stated absentmindedly. Fred and GoGo glanced at one other, each sharing the same thought.

"Besides...I thought flying makes you a better healthcare companion now. Plus you held up your end of the deal," Hiro added, still attempting to psych himself for what was about to occur.

Baymax followed Hiro's gaze towards the sky. The bot took a deep breath, enjoying the air for once. He was just glad to be out of the garage and have a nice change of scenery. Though he'd been to the garden before, everything looked different and bigger now that he was shorter.

"I do wonder at times what flying must be like from your perspective."

"Well, you're about to find out. Trust me, it's hard to describe it as anything other than awesome."

The group stopped when they stepped into Fred's private garden.

"I promise we won't destroy another wall, Fred," Hiro said, looking over at where the rocket fist had previously punched through.

"Aw, don't worry about it," Fred replied without a care in the world, "we already got the other one fixed up."

"So...what do you plan on doing now?" GoGo asked cautiously, watching as Baymax continued to fiddle with his suit.

"Fly, I guess...?" Hiro responded slowly, a butterfly passing over his head. Baymax instantly forgot about his suit, unsuccessfully trying to jump and catch the butterfly with his gloved hands.

"I can give the command for the thrusters if you want me to," Fred whispered, knowing that Baymax wasn't fond of giving Hiro orders in his current form.

Hiro nodded. He wouldn't force Baymax into doing something that he didn't want to do, especially not commanding his patient.

"You ready, buddy?" Hiro called, waving Baymax over to the team. The robot left the butterfly back to its business, running towards Hiro and nearly tripping in the process.

"...I think so," Baymax answered with a bit of uncertainty, looking up towards the sky again. It was then the robot realized how much he'd missed flying through the air since turning human.

"Climb up and put your hands and feet in the magnets," Hiro told Baymax, "make sure they're nice and secure."

It took a few tries and falls, but the former robot eventually managed to climb onto Hiro's back with GoGo's help. The teen was almost glad that the rest of the team wasn't there to watch.

"You ready?" Hiro asked once more.

Baymax gulped. "Yes."

Fred and GoGo stepped back a distance, waiting for Hiro to give the signal for take off.

"Wings," Fred said excitedly when Hiro nodded. Wings expanded instantly on the command. Hiro had to stop himself from turning every which way to get a good look at them.

Fred barely had a chance to give the second command when all of a sudden, Hiro's thrusters spontaneously decided to go off.

Before Hiro could think _"My feet are on fire!"_ he and Baymax were already zooming through the garden at top speed, breaking his promise to Fred and crashing into the very same wall that they had destroyed before with the rocket fist.

"What happened?!" Baymax screamed, his world falling and spinning around him—it was anything but 'awesome.'

Hiro was unable to answer, desperately trying to gain control of his erratic movements.

"Baymax!" GoGo yelled at the top of her lungs. "Tell him to thrust!"

"I can't!"

"Yes, you can!"

"I don't want to!"

"What do you mean you don't want to?!"

"He doesn't like giving Hiro commands," Fred explained frantically, watching in a panic as the two continued tearing through the garden.

_**"TELL HIM TO THRUST OR SO HELP ME—"**_

"Hiro! THRUST!" Baymax cried.

Hiro shot upward at last, gaining more altitude as the seconds literally flew by and they were flung towards the city.

**"TOO MUCH THRUST!"**

A sudden, eerie sense of déjà vu overtook Baymax at that moment. The robot's stomach dropped and his head swirled in tune with the spinning sky around him.

"Down! Down, down _**DOWN!"**_ Baymax screamed. Hiro obeyed and before the pair knew it, they were spiraling downwards toward the city bridge.

Baymax closed his eyes tightly, bracing himself to be hit by the many cars that were driving down below.

But just as soon as the turbulence had started, it stopped.

"Hiro?"

Silence was the only answer, and Baymax opened his eyes to see why.

It was beautiful.

The sunset glowed with an orange intensity, white clouds surrounding them every which way. A breath escaped, and Baymax looked on in complete wonder as they soared right through a fluffy ball.

Baymax reached his arm up to touch the cloud, trying to grasp it in his fingers. The cloud went right through them and he giggled, watching as Hiro strode toward the windows of a tall building.

He saw a boy smiling back at him, and Baymax realized with a double-take that the boy was himself; it was the first time in Hiro's body that he was looking at his reflection.

* * *

_The treatment is working._

Hiro could sense that Baymax's neurotransmitter levels were rising steadily the longer that they flew. The sun eventually set, leaving the two of them to soar smoothly through the stars. He had never noticed just how many there were before when they always flew low back down in the city.

Hiro landed atop one of the many wind turbines, wondering if it was the same that he and Baymax had landed on just months ago.

Baymax couldn't stop smiling. Hiro took it as his way of saying thank you.

"That was...sick!" Baymax exclaimed joyfully.

"And now you know what being sick is actually like," Hiro joked.

The two of them sat, allowing silence to reign until a question popped up in Hiro's mind that could no longer be ignored.

"Hey, Baymax...?"

Baymax turned his gaze from the glowing specks and illuminating moon in the dark sky to his patient, a smile still stuck on his face and never leaving.

"How'd you know what to do when the time came? I never downloaded flying into your system...which I should have."

Hiro remembered how excited he'd been when he had thought of the genius idea of adding wings to Baymax's suit, completely forgetting one major important feature: the actual flying itself.

"I suppose it just came to me...naturally, in a way. When the treatment started working, all that mattered was making you happy," Baymax responded softly.

Hiro nodded, listening quietly and realizing that he had just shared a similar experience with Baymax.

"Arrrrgh!"

Hiro blinked in shock at the cry of pain.

"Baymax!" The genius looked beside him to see the bot gripping his head.

"It hurts..."

Hiro attempted to perform a scan, but it appeared that his scanning feature was suddenly...malfunctioning? None of the 10,000 medical codes could figure out what had caused Baymax pain. There was no fever, just...nothing. His scanner came up blank.

What was happening?

"Do you think I can fly you back home?"

"...I think so..." Baymax gripped his head tighter when a second wave of pain washed over him.

All Hiro knew then was that Baymax needed help. Fast.


	13. Chapter 13

He was growing weaker every passing day.

The pain in his head had stopped after flying back home that night. Hiro had never been able to pinpoint what had caused the pain—not with a malfunctioning scanner. It seemed that he was growing weaker in some ways, as well.

Hiro suspected that it had something to do with turning human. Baymax was, after all, originally a robot; therefore he wouldn't have the best immune system as a human. He'd lasted a few weeks, but Hiro's body was slowly starting to give out on him—it wasn't meant to hold the consciousness of a robot.

And Baymax's body wasn't meant to hold the consciousness of a human.

GoGo had been the first to notice when Hiro did not respond quickly to a question, or when he just seemed to be "lost in thought" as he had previously told the crew so they wouldn't worry.

The episodes were small and hard to catch at first, but then they grew more and more noticeable. Fred came up with a plausible (and frightening) theory that the robot's programming was slowly taking over Hiro's humanity.

Regardless of whether Fred was right or wrong, the team had no choice but to speed up their progress with the machine.

Progress: 58%.

It was good progress for a machine that had first taken three months to complete, but the Big Hero 6 knew that they had to keep up a steady pace—or they would risk losing both of their friends.


	14. Chapter 14

Progress: 83%.

"How's he doing?" Honey Lemon asked Wasabi. The garage was open to let in some cool air, the team hoping that it would do Baymax some good.

"Tired," Wasabi answered glumly, "he can move, but it takes a lot out of him. How he has the strength to kick that thing now is beyond me."

"This is so horrible," Honey Lemon whispered sadly, watching as the bot kicked a soccer ball against the wall back and forth. He was able to stand and it seemed as though nothing was out of the ordinary, but to those who were in the know, his movements were more sluggish than usual.

"We're doing the best we can," Wasabi told her gently.

"What about Hiro?" Honey Lemon asked, worry tinting her features as she turned her gaze toward the former human. He was standing quietly by the machine, performing a thorough overview of the device. "What if we don't make it in time?"

"Don't think like that," Wasabi said firmly, "look on the bright side. The machine is almost done."

"Maybe we should tell—"

"No," Wasabi interjected, turning to face Honey, "that's the last thing we need. It's a miracle she hasn't even found out yet."

Honey Lemon nodded solemnly.

"I don't want to cause her any stress eating, either," Wasabi added, a small and joking smile crossing his face.

Honey Lemon returned the smile, knowing how Aunt Cass was when she became stressed.

"I guess you're right. What was I thinking?"

"You just want what's best for them. But right now, the best thing is to get that machine finished without any distractions."

Honey Lemon nodded again, glancing back towards Baymax.

"He shouldn't be moving too much," she noted worriedly, "I'll go tell him to stop."

Wasabi looked over at Hiro, who seemed to be done with checking the machine. "Good idea. I don't think they should be moving around too much, either. Especially not flying."

Wasabi had not been too thrilled when he and Honey Lemon had discovered that Hiro and Baymax had gone flying.

Honey Lemon understood that Baymax needed something to cheer him up, but she was scared as well when Hiro told them of the pain Baymax experienced earlier, and that his scanner was malfunctioning. The chemist had wanted to try and fix it with the gang's help, but a protective Baymax would not let them go anywhere near Hiro with tools. The genius also refused with the claim that it probably wasn't a good idea anyway, what with the risk of doing further damage.

They just didn't know what would affect Hiro in what way, so it was probably best to leave well enough alone.

"Baymax?" Honey Lemon said, gently tapping the human-bot on the shoulder. He hardly flinched, not having the strength to jump at the girl's touch. "I think you need to stop and rest."

Baymax kicked the soccer ball against the wall one last time.

"I know," he said slowly, "it's just that...in a strange way, it helps if I move a little."

Honey Lemon understood. "It takes your mind off of things for awhile," she told the human-bot, "but you need to rest and save your strength."

Baymax followed her back to the desk, sitting into his chair. He took a deep breath, cringing when he felt a pinch in his chest as the air released.

* * *

"Hiro?"

Nothing. Wasabi looked to the three Big Hero 6 members standing nearby, each stricken with a look of panic.

Baymax sat off to the side, eyes wide and fearful of the thought that Hiro was not responding, and had been staring into space for the past five minutes.

Fred clapped his hands in front of Hiro's head, finally causing the teen to blink and snap out of his stupor.

"What happened?" Hiro asked in a daze when he managed to get back online.

"It's getting worse," Honey Lemon told him faintly.

"I told you guys, I'm fine."

"That didn't look like fine to me," Wasabi said, becoming increasingly annoyed that Hiro was trying to hide his "issues" when they all knew by now that something was wrong. He got the fact that Hiro didn't them to worry, but they had to do _something._

"What are we supposed to do?"

"Get that thing finished," GoGo interrupted simply, going back towards the machine, "we're so close. Stopping isn't going to help anyone."

"Hey, what's that?" Fred suddenly asked, pointing out of the garage at what appeared to be billowing smoke in the distance.

"Looks like a fire..."

Hiro knew all too well what smoke meant.

Baymax pinched his nose, unsettled by the bitter smell.

"We have to go."

"What?"

The team turned to Hiro, dumbfounded that he would even suggest such a thing in the middle of their circumstances.

"We have to go and see if anyone needs help...the fire department might not be there yet."

"You two are in absolutely no condition to be taking on something like this," Wasabi said sternly.

"Please..."

Hiro wouldn't allow another life to be claimed by swallowing flames if he could help it.

"Alright...we'll go," Wasabi gave in reluctantly. Honey Lemon, Fred and GoGo nodded in agreement. "You two stay. This is something the Big Hero 6 needs to take care of. Well, the Big Hero 4. We'll be back as soon as we can."

* * *

Baymax couldn't help but kick the soccer ball again while waiting for a response from the team, trying not to let nerves get to him that something was going to go horribly wrong.

Hiro tried to assure him that they would be fine and return soon, but another part of him regretted letting them go to rescue victims who were possibly trapped in the fire.

Baymax's nerves were confirmed when GoGo tapped into Hiro's communicator, voice suppressed with panic.

_"We got everyone out, but Wasabi is still inside! We couldn't find him anywhere!"_

Images of the SFIT hall flashed in Hiro's mind clearer than ever before. He would not let Wasabi suffer the same fate as his big brother.

"My scanner might be malfunctioning, but the super sensor isn't."

Hiro already knew that Baymax was thinking the same thing.

_Someone has to help._


	15. Chapter 15

_Why did it have to be a fire?_

Hiro wasn't sure what was scarier; a fire at night or in the day. _Definitely night._ He now had a good idea of what Tadashi must have gone through before his death, determined to help someone in need when others were unable—and it wasn't pretty.

The building was going to collapse on them at any minute. It had managed to hold out so far, but it didn't take a genius to know that they had to hurry.

The flames weren't out of control yet, but they were getting stronger every second. He could barely register the fact that Baymax had refused to stay out of the building and was clinging onto his back for dear life.

Hiro was just glad that the human-bot was wearing his supersuit, which helped to fend off the heat and provided some oxygen against the dark smoke that clouded his vision. Thankfully though, he had his super sensor that was—surprisingly—activated on Baymax's command when they first entered the flaming building.

Wasabi was close, according to the sensor. His teammate had already been scanned by Baymax once before, so he had at least some data to go by without having to scan him again.

Hiro could just make out a shape trapped underneath heavy fallen debris, coughing and struggling to break loose. He would have laughed at lifting such a large amount of weight if it hadn't been for their current situation and the body he was stuck in.

"What are you doing here?!" Wasabi shouted in shock when Hiro managed to set him free.

"No time to explain! Are you hurt?"

Wasabi shook his head at the nurse's odd question, knowing that Hiro was still unable to operate his scanner. "Let's go!"

Hiro moved quick as he could, Wasabi just in front of him and Baymax still attached to his back.

He stopped short upon hearing a cracking sound above him.

Realization hitting him, Hiro instantly pulled Baymax from the magnets and into his arms, tossing the frightened human to the side and calling for Wasabi.

Wasabi ran to Baymax, checking the bot for any injuries that he could have attained in the throw. Baymax only shook his head, stunned. The suit had, luckily, protected him against scrapes and bruises.

It was all happening too fast.

Baymax had just enough time to look up, horrified, to see a damaged beam creak and land...right on top of Hiro.


	16. Chapter 16

_**"HIRO!"**_ Baymax screamed, trying with all his might to pull away from Wasabi's grip. His body seemed to forget all of the tiredness that he had been experiencing the last few days.

"Let me go!"

"There's nothing you can do!" Wasabi shouted, keeping a firm hold. "We have to go. NOW!"

"We can't just leave him!" Baymax cried, terror instilling when rubble began crashing down.

Finally, he yanked himself free of Wasabi's hold and ran as fast as his burning legs could carry him back towards the fallen robot. It didn't matter that everything was about to come crashing down. All that mattered was getting to his patient, even if there really was nothing he could do to help.

It was no longer up to the codes or protocols of a tiny, yet advanced medical chip.

Wasabi stood in place for a moment, eyes widening when he realized that Baymax had gotten loose. Looking up, he saw that the roof was beginning to crumble.

"...I'm so sorry..."

He ran in the other direction towards the open door.

* * *

"You came back."

Hiro couldn't believe it. Even without his programming telling him that he had no other option but to _help_ his patients, Baymax had decided with his own free will to come back—and inside a collapsing building, of all things.

"...Of course I did."

"I thought you said that you never would have come back for me." Hiro clearly recalled their past argument in the garage.

"Someone once told me that it's human to make mistakes."

"Very funny...now go. Get out of here."

"I can't..."

"You have to."

"No..."

"It's okay, Baymax. I'll be fine. It doesn't hurt..."

"No! I'm not leaving you here!"

"Baymax...are you satisfied with your care?"

"Please, don't...don't say that...I'll find a way..."

"Look at me."

Baymax looked. Hiro was pinned mercilessly underneath the fallen beam, his body completely covered except for a small bit of his chest and head. A torn vinyl arm lay next to his side, his red suit completely bruised and battered. Sparks flew off from his mangled rocket fist.

In his aching heart, Baymax knew that there was no way he could be saved.

"Hiro, I'm not leaving you...you—you're my..."

What? Patient? Hiro didn't care what Baymax thought of him as anymore. He only wanted to see the human out of the building unharmed.

_Your health is my only concern..._

"...Friend. My best friend...you always were."

Something wet trickled down the bot's face, the same kind of wet that he had experienced while remembering Tadashi.

Hiro was sure he felt then, even though he really couldn't. It was a warm but pleasant feeling, very unlike the scorching flames closing in on them.

Baymax started to cough, the smoke finally getting to him through the suit's mask. Hiro could tell that he wouldn't be able to last much longer, especially not in his current condition; it was a miracle how long he'd been able to hold on so far.

"Are you satisfied with your care?" Hiro repeated.

A second bout of déjà vu overtook Baymax. It was as if they were back in the portal, an experience that neither were fond of reliving.

"I am not satisfied with my care..."

That stubborn robot.

"Th...there's no—"

Baymax gripped Hiro's white, free and undamaged hand tightly as he could. Hiro returned the gesture, surprised when Baymax allowed his touch without a cringe or a jump.

_Do you trust me?_ Brown eyes seemed to ask.

Hiro nodded without hesitation, wondering why Baymax would even ask him such a question.

_With my life._

Then everything went black.


	17. Chapter 17

"I...I left them in there," Wasabi said regretfully as he and the group stood outside of the failing building. He was never going to forget running in the other direction, never looking back to see if Baymax had somehow managed to get Hiro out. "I ran. They went back for me and I ran and left."

Honey Lemon placed a gentle hand on his shoulder, tears threatening to fall even harder. Wasabi continued staring at the building, eyes reflecting a guilt almost worse than the flames themselves.

"...There was a beam. It fell on top of Hiro and I tried stopping him, I really did, but Baymax ran after him...it's all my fault!"

"There wasn't anything you could do," GoGo said calmly, though on the inside she was screaming. After all they'd been through together, it was over and two of her friends were gone. She didn't blame Wasabi and never would—two more lives consumed by a raging blaze. Just like that. They were so close!

Wasabi sighed mournfully, still unable to accept the fact that he'd abandoned his friends in their greatest time of need. He was no longer fit to be part of the Big Hero 6, and maybe he never had been in the first place. They couldn't even _be_ called the Big Hero 6 now because of him. He was just as bad as Callaghan, if not _worse_ than the professor they thought they could trust. He would never forgive himself.

But Fred was the first in the crowd that had formed to notice a small shape moving slowly toward the building's opening.

"Wait...I think I see them..."

The gang half expected to find that both of their friends had triumphantly escaped the collapse, but only Baymax appeared through the smoke.

To say that the robot-turned-human looked terrible would have been an understatement. His purple suit was no longer purple but a blackish gray, ash covering his face from under the mask. He held his chest with one hand, his other hand clasped tightly around a hidden object.

"Baym—Hiro!" The team cried all at once, earning confused glances from nearby onlookers at the name's mix up.

Baymax wheezed and stepped out of the burning building. Coughs wracked his poor, tiny body as he found extra strength to move quickly as possible away from additional bursts of fire. Then he dropped, fainting on the spot—but not before murmuring something indecipherable and gripping his hand tighter around the unseen object.

The crowd gasped, yelling for help.

Wasabi and the team immediately ran up, pulling the fallen bot to safety just before the ceiling caved in.

GoGo knelt to her knees and checked for a pulse, sighing in relief when she was able to find one. Then she gently unfurled the bot's clenched hand, eyes widening in disbelief when she discovered what Baymax had rescued from the fire.

Wasabi nearly fainted along with Baymax when he was met with the sight of an intact, shiny and green little medical chip.


	18. Chapter 18

_What? What's this? This story has officially reached 100 reviews? I never even thought it would get 1! xD No, this is a huge milestone for me since it is my first multi-chapter fic, and my first story to reach 100! I don't know what else to say except...thank you, everyone! :D I never thought it would be this successful, especially not with such a weird and random plot that popped into my head one day (no idea where it came from xD) Unfortunately, as excited and sad that I am about it, the end is almost here. Maybe one or two more chapters after this and "Differences" will come to an end! Thank you so much for all your support whether it be reading, reviewing, following or faving! =)_

* * *

Progress: 100%.

_...The building collapsed, but the Big Hero 6 were able to pull out fire victims trapped inside. According to crowd reports, child prodigy Hiro Hamada went in to rescue a teammate and came back out burn free, but was overcome by smoke. He was immediately taken to the hospital for smoke inhalation treatment and now appears to be in stable condition. No further information has been released at this time._

Baymax had known what he'd had to do from the moment it was apparent that he was never going to get Hiro out any other way. It was frightening and the very last resort he wanted to risk, but it was a risk he had to take.

"It was hard."

Baymax didn't like going into too much detail about what happened in the building; at least not out loud. The images of flames and smoke singed his mind, and the bot knew that he wasn't going to be forgetting the near tragic incident anytime soon—not even as a robot. He could still feel like he'd recently escaped the surging fire, imaginary heat threatening to envelope him once again.

The last thing Baymax wanted was to be sent into another panic attack; he knew he wouldn't be able to handle one without Hiro, even though the team was still with him. He did his best to shove the images into the back of his mind.

The tiredness had returned soon after he'd recovered in the hospital. His weakness hadn't caused too many questions to rise among medical personnel. He had, after all, just outrun a raging inferno.

Baymax shifted slightly underneath Hiro's bed covers. He couldn't remember much else of his stay at the San Fransokyo hospital, but it was good to be back in a familiar place—back _home._

"I don't know how you did it, but you did. Hiro is safe thanks to you."

Baymax gave Wasabi and the rest of the group a weak smile, glancing down at the chip cupped gently into his hands. His smile faded.

_Not completely safe._

"We're going to get him back," GoGo said firmly, "if Hiro was able to rebuild you, we'll be able to rebuild him...okay, that sounded really weird."

"I believe I'm getting used to all this 'weirdness' by now," Baymax chuckled, never wanting the green card to leave his sight.

"And now that the machine is done, you guys can go right back to the way things were," Fred added cheerfully.

The team had managed to finish the rest of the device without the aid of Hiro. Baymax had even given them a friendly reminder not to build the machine's case with glass again, instead replacing it with a material that wouldn't give anyone a cut on the foot or cause a life-threatening explosion.

Baymax nodded, content with the fact that things would return to normal soon, though some part of him begged to differ.

They had everything they needed to rebuild another "Baymax." But...what if Hiro wasn't the same? What if pulling out the chip had overwritten Hiro's human nature, like Baymax had feared the first time his friend had been deactivated? If Fred had any of his theories on the matter, he wasn't sharing them. It was rather out of character for him and left the bot with the feeling that something was going to go horribly wrong again.

A knock on the bedroom door sounded and Aunt Cass made an appearance, poking her head inside.

"Can I get you anything?"

"No thank you, Ms. H. We were actually just going to let him rest," Fred answered for the group. They nodded, starting to leave the room.

Aunt Cass smiled, following them out to say goodbye.

Wasabi stayed behind until the rest were gone. He turned back to Baymax.

"I—I'm so sorry for leaving like that. I just—I didn't know what else to do—"

Wasabi stopped when Baymax placed a free hand on his arm. He glanced down at the human-bot to see an expression that took his breath away—forgiveness.

No words were needed to explain that Baymax was forgiving someone who had left him in a collapsing building to die.

Baymax gave him a smile. A real, genuine smile.

_It wasn't your fault._

Wasabi felt a weight being lifted off his shoulders. He smiled back.

* * *

"I'm sorry about Baymax, sweetie," Aunt Cass said when she returned, looking over at the robot's empty charger and back to her nephew's chip in Baymax's hands.

"It's okay, Aunt Cass...if I rebuilt him once, I can rebuild him again," Baymax replied in the words of GoGo. On second thought, maybe he hadn't gotten used to all the weirdness yet. At least he'd finally gotten the hang of saying Ms. Hamada's name right.

"That's the spirit. I'm just glad you're okay. You know how this superhero business gets me all wound up." Aunt Cass laughed, taking a piece of chocolate doughnut that she had brought with her and popping a piece into her mouth. She held it out in front of Baymax. "Want some?"

Baymax hesitated. He'd never had a doughnut before, but Hiro would probably want him to try one. He nodded and Aunt Cass gave him a small bit, standing from Hiro's bed to head back out the door. He chewed slowly on the doughnut, deciding that it was his new favorite human food next to milkshakes.

Then he realized that he was left alone for the first time—but not really. He still did have Hiro with him, in a way. His friend was just in stasis mode like he himself had been when left behind in the portal, or Abigail in the pod.

Mochi suddenly hopped onto the bed and made himself comfortable on his stomach, curling up into a ball to fend off any nightmares or doubts of Hiro's memory that would plague the bot.

Baymax turned off the lights, reluctantly placing the chip on the desk beside the bed. He stroked Mochi as his eyes began to droop, never straying from the chip.

Hiro wasn't _gone, _just sleeping...and he would wake up soon.

_I promise._


	19. Chapter 19

It was ready.

"Baymax" was ready.

The team asked if he wanted them there...just in case. Baymax told them that he needed to do this alone.

Taking a deep breath, he took one last look at the chip in his hands, seeing his creator's name.

He placed the chip back into Hiro's chest, back where it rightfully belonged.

"Owwww...?"

"Hello. I am Baymax, your personal healthcare companion. I was alerted to the need for medical attention when you said 'ow.'"

"...Hiro...?"

Baymax waited.

Seconds passed and there was no response.

Minutes passed and there was no response.

"On a scale of one to ten, how would you rate your pain?"

_No._

"Hiro..."

"My data indicates that the individual standing in front of me is Hiro Hamada. Are you referring to another Hiro?"

"Yes."

"Would you like me to try and locate this patient?"

"Yes."

"Hiro is here."

"Yes. You are Hiro."

The second Baymax blinked, tilting his head slightly in confusion.

"I am Baymax, your personal healthcare companion."

"No...you are Hiro. Hiro Hamada."

The second Baymax blinked again, attempting to process what Baymax had just told him.

"Do you remember building this machine?"

Baymax walked to the body swapper, legs turning into jelly.

"We switched bodies. I'm a robot. A healthcare companion. You're human."

The second Baymax remained silent for a few moments. Baymax's heart thudded in his chest, his stomach full of non-literal butterflies.

"Such a phenomena would be entirely impossible."

"Not for you. Fred was the one who gave you the idea, remember?"

The second Baymax went silent once more, a blank stare continuing to process the information.

"Fred, GoGo, Honey Lemon, Wasabi. They're all waiting for you."

The second Baymax blinked again; twice this time. He remained silent, allowing Baymax to continue talking.

"Ms. Hamada—Aunt Cass...we've been hiding this from her the entire time, because otherwise she'd eat the whole café."

Baymax took a step forward. The second Baymax remained frozen in place.

"Mochi is waiting, too," Baymax went on, "you might not get along all the time, but I know he still loves you even after throwing him up the stairs."

The second Baymax blinked once more, taking a step back. Baymax followed him forward.

"Tadashi. My creator. Your big brother."

The second Baymax blinked three times, as if he were malfunctioning in some way. He took another step back, Baymax taking one step forward.

The human-bot held out a hand.

"...And me. Baymax."

The second Baymax stood in place again, unmoving and processing the hand in front of him.

"Remember this?" Baymax asked, reaching his arm out a little further so the second Baymax could better grab hold.

"Fist bump is not in my fighting database."

Despite the situation, Baymax felt the odd need to facepalm. He continued to hold out his hand anyway, his arm beginning to shake. Whether or not it was from the fact that this Baymax remembered a simple fist bump, his arm was tired or he was growing continuously weaker, it didn't matter.

"No, this isn't a fighting thing," Baymax explained with a small grin, "it's what people do sometimes when they're excited or pumped up. I could never get it right, but who knows..."

The second Baymax reached his arm out slowly, slapping Baymax's outstretched hand once, then twice. Baymax offered his fist and the second Baymax balled up his own.

"Bah-a-la-la-la!" The two said simultaneously. Baymax let out an amused sigh.

_Some things never change._

"Hiro is here."

It was like the command to destroy had been given.

"What?"

"Hiro is here."

Wet began to stream down Baymax's face, but the tears were hardly noticeable through the realization that Hiro was never going to come back.

"No..." Baymax said, his voice cracking. "He's not here. He's gone..."

Arms suddenly wrapped themselves around the bot without warning.

"There, there. Crying is a natural response to pain."

"This...this is a different kind of pain."

_"...Friend. My best friend...you always were."_

Baymax gently unwrapped the arms around him, readying himself to leave the garage and relay the bad news to the four waiting. He lowered his gaze to the floor, numbness seeping its way into his being.

He stopped short, lifting his head up suddenly when a voice interrupted his steps, a voice that was still mechanical, but had at last regained some amount of humanity.

"...You're my best friend, too."


	20. Chapter 20

Baymax's tear-stained eyes widened and he spun around in disbelief, almost falling flat on his face in the process.

"Hey, buddy," the second Baymax waved.

He would know that voice anywhere, mechanical or not.

"Hiro!"

Baymax immediately ran to the newly awakened genius, throwing his arms around the giant marshmallow and nearly outshining Aunt Cass in who could give the most suffocating hugs—not that he _could_ suffocate. It definitely surprised him, what with how tired Baymax had been feeling lately.

"I—I thought you left me..."

"It's okay...I'm here for real. Now enough with all this mushy stuff."

Baymax only hugged tighter, never wanting to let go should Hiro suddenly slip away again.

Despite himself, Hiro wrapped his arms around the bot in return, squeezing gently and closing his eyes in content.

"Thanks for not giving up on me."

"We fixed the machine!" Baymax exclaimed, glancing up with a bright smile.

"Really? I'm gonna have to take a look at it. Just to be safe." A thought struck Hiro and he released Baymax, looking about the garage for any changes besides the completed machine.

"Aw, man. How long was I out?"

"Long enough," Wasabi's voice called, the Big Hero 6 coming into view.

"You really had us worried there, dude," Fred said, relieved when Hiro and Baymax appeared to be alright.

"Baymax snapped me out of it. I wouldn't be here right now if it wasn't for him."

Wasabi ruffled Baymax's untidy hair, earning a playful (but gentle) shove from the bot in return.

"We're so glad you're back," Honey Lemon said excitedly, pulling on Hiro's arm to drag him towards the body swapper.

"Look, look, look! It's done!" she practically squealed.

Hiro eyed the square, black case resting in the middle of the floor, an assortment of blinking lights meeting his gaze.

It was hard to believe that a small case had once taken three months to complete. It wasn't so much the design that had taken so long, but all the twists and turns inside of it that had needed great attention to detail. Rubber tubes attached themselves from either side, slithering along the floor like snakes. Metal headsets rested at both ends, glinting in the light.

Hiro had invented the headsets in such a way that they would shrink or enlarge depending on their wearer, but what befuddled him the most was the fact that neither he or Baymax had been wearing a headset during the explosion. In the end, he figured that the intense power it charged on was to blame in their transformation. They _had_ been caught in the middle of it, after all.

"We have to get rid of this thing."

"I hope you mean after changing back," GoGo muttered.

"What? You mean I can't try it out?" Fred pouted, picking up a headset.

His question was met with total silence, the Big Hero 6 glaring at him.

"...What? I can't switch bodies with a lizard? Not even a regular one?"

"Get over here, Fred," GoGo said, grabbing the headset from the science enthusiast and giving it to Hiro.

"Not even a sandwich?"

"I have some concerns," Hiro said to Baymax. The human-bot just shook his head with a small, amused grin.

* * *

"Looks like we're good to go," Hiro said once his routine check was complete, turning to face the Big Hero 6. He blinked, attempting to find the right words for just how...amazing they all were.

"Thanks, you guys...for everything. We couldn't have done it without you."

"Don't mention it," Wasabi replied softly, "it's what friends do."

GoGo, Honey Lemon and Fred nodded in sync to Wasabi's statement.

"Anything else you wanna try first before going back to normal?" Fred couldn't help but ask, curious at How Baymax would answer.

"I guess it wouldn't hurt to have one more milkshake," Hiro added thoughtfully, wanting to give Baymax a last say in the matter. "That's probably the first thing I'm gonna have, actually. Either that or gummy bears." Hiro hadn't realized just how much he missed eating.

Baymax paused in his endeavour with Mochi, clicking off the laser in his hands. The cat blinked in confusion when the red dot on the floor vanished, tapping the empty spot with a paw and meowing in annoyance.

"Thank you, but...I think I've had a share of humanity that will last me a lifetime," he answered the group honestly with a little laugh.

"Perfectly understandable," Hiro agreed, glancing at the machine and back to Baymax.

"Ready, buddy?"

Baymax nodded nervously, standing up from his usual seat to go towards the machine. Hiro placed his headset where it rightfully belonged, handing Baymax the second helmet.

Just when the bot was about to reach up to put on the device, the garage door decided to open.

"Hey, Ms. H!" Fred greeted the café owner as if it were the most casual thing in the world.

"Hiro? What's all this?" Aunt Cass asked, glancing about the garage and gesturing to the machine.

Hiro wasn't able to resist. He had to facepalm.

"...There's something we should tell you, Aunt Cass," he began slowly.

His aunt's eyes widened when she spotted her nephew and Baymax with their headsets.

She dropped.

"Uhhhh, I think she just put two and two together," Wasabi noted in surprise.

Hiro waddled to his aunt, taking off his helmet.

"You have fallen," he stated simply.


	21. Chapter 21

"She'll be fine," Hiro told the group as they pulled the fainted Aunt Cass away from the machine, "just a bit of shock."

"A bit?" GoGo remarked.

"It's probably better this way."

Hiro turned to Baymax, but stopped when the bot appeared to be in some kind of distress.

"Baymax?" Hiro asked cautiously, fighting against the protocol to put his new and improved scanner to use. He couldn't risk falling back into the thousands of codes, not when they were minutes away from returning to normal.

"It's hurting again," Baymax answered, holding his head and squeezing his eyes shut in pain.

"Is it safe?" Wasabi gestured to the machine, worried for the bot's safety. If he was in pain, then maybe the change wasn't such a good idea yet.

"We have to go through with it," Hiro replied, although he wasn't so sure himself. "The longer we stay like this, the worse it gets."

As if on cue, Baymax collapsed for his second time since the fire, and almost as suddenly as Aunt Cass. Hiro barely managed to catch him in his arms, dropping his helmet. He lifted the bot carefully, cradling him gently as possible.

"Baymax!" Honey Lemon cried.

Hiro sensed the robot's heart faltering. It was quickening at an alarming rate, his eyes fluttering.

_Not now, not now!_

"What do we do?!" Fred asked, too much in a panic to come up with a theory on the subject.

"Get my helmet and get the other one on him," Hiro ordered, "we have to do this."

"But what if—" Wasabi started, concerned that the swap would cause further damage.

_**"NOW!" **_Hiro strained his everlasting robotic tone.

Fred didn't need to be told twice, picking up Hiro's fallen helmet in a frantic motion, placing it on top of the soft vinyl material. Honey Lemon ran for the remaining helmet while Wasabi double checked and made sure that Aunt Cass was at a safe distance from the machine.

"Come on buddy, stay with me," Hiro pleaded when the bot's eyes began to slide shut, his heart rate continuing to falter.

Honey Lemon grabbed the remaining helmet, giving it to Hiro. The genius reached with one arm to place it on Baymax, but paused. What if Wasabi was right and the machine only ended up hurting him more? He shook the thought away when Baymax's eyes closed, resting the helmet tenderly upon the mess of hair.

GoGo readied herself to flip the machine's switch on Hiro's command.

"Get back," Hiro said to the other three, taking one last look at the human Baymax.

_I can't lose you again..._

He nodded.

GoGo flipped the switch and there was a buzz, a flash of light.

Then the power went out.


	22. Chapter 22

_Wow, 5 chapters later and I actually finish my first multi-chapter fic! o.0 Of course, I never would have made it this far without all of you readers! For the last time, I would like to say a big thank you to everyone who has read, reviewed, followed or favorited this fic! Thank you so much! You're the best!_

* * *

Just as soon as the lights went off, they turned themselves back on. The team had to blink to adjust in the sudden brightness, glancing around the room in worry to find their friends.

GoGo heard breathing, like someone was hyperventilating. She turned to look at the machine, seeing the figure of Baymax on his back and a human boy flopped onto his stomach next to the device. The kid was trying to get his breath back, eyes closed and head bobbing up and down in tune with his falling and rising chest.

The helmets lay on the floor to the side, having fallen off during the power outage.

"Did it work...?" Wasabi asked quietly, about to get up to try and help.

GoGo stopped him, raising an arm so he couldn't get by her. The four Big Hero 6 members watched the scene unfold before them, each wondering the same thing.

"I need you to breathe," the white marshmallow said to the boy with a cybernetic tone intact, "can you do that for me?"

"Hiro" shook his head, eyes still closed and head still bobbing up and down. He grabbed at his throat and "Baymax" wrapped soothing arms around the boy, which seemed to help calm him down.

"Breathe," the robot instructed, "in and out. In and out."

The teen followed his orders well, and once the process repeated and he was able to breathe on his own, his eyes slowly opened.

A wide smile spread and he started laughing, a bright and joyful sound that resonated throughout the entire garage. He threw his arms around Baymax and the bot hugged back, wrapping his arms tighter around the newly robot-turned-human.

"It worked!" Hiro exclaimed in his voice. _His_ voice. Not Baymax's. The real, human voice that he had been born and raised with. Sliding off of his robot's puffy stomach, he bounced onto the hard garage floor. He shook his head in a daze, but regained himself quickly to try standing up. His legs wobbled and he almost toppled back over, but safe and familiar arms prevented his fall.

"Thanks, buddy," Hiro said gratefully, leaning into the bot's hold as his legs attempted to give out on him again. "Spending almost an entire month as a giant marshmallow will do that to you. No offense." Hiro was just glad that it hadn't been three months.

Baymax blinked, pausing in thought.

"None taken."

Hiro grinned and he could have sworn that Baymax grinned back, remnants of humanity still etched within his coding.

The rest of the Big Hero 6 came into view, relieved to find that the change had worked.

"Never do that again," Wasabi scolded Hiro tiredly.

"I don't think we ever will," Hiro confirmed. He sighed in relief at the fact that he could actually, finally sigh once more. If air was like sand, he would kiss the invisible element like survivors stranded at sea. He glanced down at his original body, still thankful that the machine was able to change him back with clothes on.

"Okay, okay," he said to Baymax, "scan me. Just to be sure."

Baymax happily complied, relishing in Hiro's command when his scanner seemed to be perfectly operable with no issues from the change.

"It appears that the transformation has indeed succeeded and you and I have switched back to our respective forms."

Hiro held out a hand, a smirk crossing his features. Baymax reached his forward in response.

"Bah-a-la-la-la!" the robot exclaimed. Hiro was just glad that he could do a fist bump the right way again, though Baymax's signature bump never failed to be just as awesome as flying.

"Your neurotransmitter levels have risen dramatically. This indicates that you are very happy."

"I am, I really am."

It was like he'd just eaten a huge amount of sugar and it was buzzing in the back of his brain; Hiro figured it was because his emotions were held at bay for so long. He hoped that Baymax wasn't experiencing some type of withdrawal from said emotions, but it seemed that the robot was already recovering from his time as a human being.

Hiro was just glad that his own heart was back to its normal, healthy pace and that Baymax was no longer in any pain. The fact that he could have lost his best friend—and permanently—was a scary thought.

Looking about the garage, it also appeared that the machine hadn't exploded. At least there wasn't glass everywhere like the first time.

"Man, that was SICK," Fred commented. Honey Lemon stood by, holding a skittish hairy baby in her arms. The cat must have followed the group to seek shelter from the impending power outage. Hiro was, once again, just glad that Mochi hadn't interfered in some way. Who knew what life was like as a cat?

"It's okay, Mochi," Hiro said calmly. The calico meowed and squirmed from Honey Lemon's hold, surprising Hiro when he decided to rub against his legs, an action he hadn't executed since being thrown up the stairs.

Green eyes smiled up at brown and Hiro extended his arms, picking up the fluffy creature. Mochi didn't resist, snuggling into Hiro's chest. The genius stroked patched fur in shock, appreciating the soft feel. He glanced up at Baymax and the robot tilted his head in a knowing gesture.

A pinch from Fred completely ruined the moment, causing Hiro to let go of Mochi. The cat dropped on all fours, scampering away from Hiro and running out of sight.

"Dude! Ow!"

"Just making sure that this isn't a dream," Fred explained, trying to get a good look at Hiro's pinched arm.

"Baymax already scanned me!" Hiro argued, exasperated and wondering why in the world Fred hadn't just pinched himself to see if it was all a dream.

"Ugggh..."

"Uh, guys?" GoGo called, motioning towards Aunt Cass. "I think she's waking up..."

"We can't let her see the machine," Hiro said anxiously, not wanting to subject his aunt to her stress eating. "Baymax, let's take her back in the house."

Baymax shuffled to Aunt Cass, lifting her gently when a sudden growl sounded.

The Big Hero 6 turned to Hiro, following their ears towards his stomach. He smiled sheepishly.

"Gummy bears, here I come."

* * *

"Would you do the honors?"

Baymax, donned in a brand new red and shiny supersuit that Hiro had created as a replacement for the one lost in the fire, nodded in quick agreement and took one last look at the body swapper before him.

Hiro grinned, standing by the robot in his own supersuit. He paused for a moment, wondering if it was right for him to choose his next words. He shook the thought away, knowing that this time was entirely different from the last that he had used the haunting command.

"Baymax. Destroy."

Baymax had never been happier to hear those two words in his life, drawing back an arm in a swift punching motion.

The machine shattered upon impact, a new and different kind of glass flying in all directions that wouldn't cause any physical damage like a cut foot. It comforted Baymax in a way to know that the Callaghan incident was no longer his last time hearing the directive.

A crying sound was heard seconds after the machine was destroyed. Hiro and Baymax turned to see Fred sobbing on Wasabi's shoulder.

GoGo rolled her eyes. "Woman up."

With help from the Big Hero 6, the garage was cleaned up in no time. Aunt Cass had come back down to visit and offer doughnuts, claiming that she just had the weirdest dream ever and looking back and forth from Hiro to Baymax.

Hiro politely declined a doughnut, stomach full of delicious and very much missed gummy bears.

"So...what now?" Honey Lemon asked Hiro curiously, thanking Aunt Cass for the doughnuts as she exited the garage. The café owner searched for evidence of the machine, unable to find any.

"Last hug," Hiro said before his aunt could leave, wrapping his arms tightly around her.

Popping another doughnut into her mouth, she disappeared from sight.

"Besides a ton of homework that I have to catch up on?" he answered Honey Lemon, cringing at the thought and glancing up at Baymax. If the genius didn't know any better, it appeared that the robot was having a staring contest with the plate of doughnuts.

"What do you say, buddy?"

Apparently the bot already had something in mind, answering quickly and snapping his attention away from the doughnuts.

"Flying still makes me a better healthcare companion."

Hiro looked back at his teammates. "Wanna go for a spin to celebrate?"

Wasabi shook his head, unsettled at the idea of heights. The others followed suit, but for different reasons.

"You guys go. We'll catch up with you later."

* * *

The inseparable duo landed once more on one of the many wind turbines of San Fransokyo, enjoying the beautiful view and the fact that they were both finally back to normal, back in their original bodies where they belonged.

"Hiro?"

"Yeah?"

"Your health is no longer my only concern."

Hiro took advantage of the moment to use his returned ability to smile up at Baymax, turning his gaze back to the orange sunset ahead as a familiar, pleasant warmth filled his chest.

_Sometimes life doesn't go the way you plan, but looking at it from a new angle as my brother always said—especially through the eyes of a friend—can definitely help make a difference._


End file.
